Steam turbines such as the high pressure steam turbines used in nuclear power plants typically are constructed such that the outer structure or casing of the steam turbine is joined along a horizontal joint. In order to ensure good efficiency and proper alignment of the inner rotating components of the steam turbine, it is necessary that the mating surface of each section of the outer structure along the horizontal joint be flat within a very narrow tolerance. However, due to the large size and weight of the turbine assembly, it is relatively difficult to machine these surfaces to the required tolerance while the components are being fabricated. Moreover, as known to those of ordinary skill, even if the required flatness is achieved in a machine shop, the dimensions will most likely change after the components are installed on-site. Additionally, in the case where a steam turbine is undergoing retrofit, maintenance or repair, the disengaged surfaces of the horizontal joint will most likely be out of tolerance and it will be impossible to reassemble in this condition. This latter out of tolerance condition arises due to the effects of thermal and mechanical stress, hysteresis, creep and other phenomena which permanently deform the assembled components.
Therefore, it would be desirable to provide methods and apparatus that permit the horizontal joint surfaces to be machined at any desired site. Such techniques should be applicable to both new turbines about to be installed, as well as to retrofits and turbine maintenance operations that require opening the turbine along the horizontal joint.